Economic Viability of Companion Planting in the Face of Virus Yellows in Sugar Beet[Viabilité économique de la plante compagne face à la jaunisse de la betterave sucrière]

Following the EU decision to ban neonicotinoids in 2018, several alternative solutions have emerged from the dedicated French national research project initiated in 2020. Companion crops, such as barley or oats, sown at the same time as beet, have a repellent effect and reduce aphid numbers on sugar beet plants. This paper examines the sustainability of implementing these ecosystemic plantings to reduce the economic risk of virus yellows infection in sugar beets. We show that while the companion plant may be effective in repelling aphids, the strict economic impact of aphid number reduction is mainly negative under benefit/costs assumptions currently accepted. Our analysis is based on the incidence model developed by Qi et al. Planting oats or barley hinders the optimal development of sugar beet and, according to experts, reduces its production level by a minimum of 3%. To mitigate this negative effect, it is necessary to destroy the companion plant at the 2-6 leaf stage, inducing additional costs to the planting costs. Finally, the expected reduction in aphid numbers is about 35%, which does not necessarily translate into a 35% reduction in virus yellows losses. As a consequence of our analysis, it is required to develop research in two directions, (1) analyse the potential of additional benefits of ecosystemic plantings to the strict impact on aphid number reduction and (2) analyse the potential benefit of synergy between this measure and other ecosystemic methods.